1. Field of the Invention
The present invention generally relates to a wire electric spark machine in which discharge is generated in a fine gap between a wire electrode and a work with a processing liquid as a medium so as to progress the working on the work, and particularly relates to an improvement of a wire guiding device in the wire electric spark machine of the type mentioned above. 2. Description of the Prior Art
FIG. 1A is a diagram for explaining a wire guiding device in a wire electric spark machine, and in the drawing, the reference numeral 1 designates a wire electrode, 2a and 2b designate die-shaped wire guides for supporting and guiding the wire electrode 1, and 3a and 3b designate power supply members for transmitting electric power from a working power source (not shown) to the wire electrode 1. A clearance between the wire electrode 1 and each of the wire guides 2a and 2b is generally set to about 2-10.mu.m. As shown in FIG. 1A, the power supply members 3a and 3b are generally pressed by the wire electrode 1 at portions above and below the wire guides 2a and 2b respectively, so that the wire electrode 1 is bent by an angle .alpha. at each of the wire guides 2a and 2b.
The respective states shown in Figs. 1A and 1B are generally called a straight working state and a taper working state respectively. The operation in the taper working will be described hereunder. It is possible to slant the wire electrode 1 by moving the wire guide 2a horizontally as shown in FIG. 1B. The taper angle .theta. of the wire electrode 1 is caused owing to a relative movement between the wire guides 2a and 2b and is variable corresponding to the amount of the movement. In this case, the positional relationship between the power supply member 3a and the wire guide 2a and that between the power supply member 3b and the wire guide 2b are not changed.
The wire guides 2a and 2b are generally made of jewelry such as a diamond, die-shaped, and made very small in size (a radius of curvature is also small). Further, the wire electrode 1 is large in its flexual rigidity, so that when the wire electrode 1 is actually slant by an angle .theta. as shown in FIG. 4B, bending deformation is caused in the wire electrode 1, resulting in an error .epsilon..
FIG. 3 is an enlarged diagram showing a wire guide 3, and the reference numeral 3a designates a diamond, and a straight portion of about 0.2-0.3 mm acting as a guide portion is formed at the central portion of the wire guide, and the taper angle is made gradually enlarged from the straight portion so that the wire may be inserted easily (Japanese Patent Unexamined Publication (Kokai) 150934/1980).